Hexetidine, which is an amino-hexahydro-pyrimidine derivative, is a broad-spectrum antibacterial, and has been formulated in a number of products including mouthrinses (Oraldene, Sterisil) and dentifrices (Mentadent-P). U.S. Pat. No. 2,837,463 discloses therapeutic compositions, including mouthwashes and dentifrices, containing said hexahydropyrimidine antibacterial compounds. British Pat. No. 771,768 also discloses dental therapeutic compositions containing a 5-methyl-5-amino-hexahydropyrimidine compound, said dental compositions including pastes, powders, liquids, chewing gums, tablets, lozenges and troches.
The 5-aminohexahydropyrimidines and a process for their preparation is disclosed in U.S. Pat. No. 2,387,043 which is incorporated herein by reference.
The use of hexetidine (5-amino-1,3-bis(2-ethylhexyl)-5-methyl-hexahydropyrimidine) as an optional antibacterial additive in oral compositions is known in the prior art as disclosed in U.S. Pat. Nos. 3,622,661; 3,984,537; 3,989,814; 4,490,353; 4,528,182; and in British Pat. No. 1,533,634 and No. 1,461,896.
U.S. Pat. No. 4,522,806, European Patent Application No. 049,830 and British Pat. No. 2,084,870 disclose oral compositions containing hexetidine, and zinc salts for the inhibition of dental plaque without staining the teeth in an aqueous oral vehicle containing glycerin and optionally, a fluoride compound.
However, attempts to formulate a stable antiplaque dentifrice based on these ingredients using glycerin, the most common dentifrice humectant, have been unsuccessful. Glycerin formulations were soft, and separated during the accelerated aging tests. It has been found that when a polyethylene glycol humectant is used, formulations can be prepared which are cosmetically stable and successfully pass the accelerated aging tests.
Furthermore, it has been difficult to formulate a dentifrice containing hexetidine (5-amino-1,3-bis(2-ethyl hexyl)-5-methyl-hexahydropryrimidine), zinc (Zn++), and fluoride (F-) in which available hexetidine is minimally inactivated or decomposed, and soluble zinc (Zn++) or fluoride (F-) is minimally complexed or lost, due to interaction with formula ingredients. In order to overcome this problem, it has been found that by combining a surfactant selected from the group consisting of anionic, nonionic, zwitterionic or mixtures thereof as the solubilizer for the water insoluble hexetidine, employing as humectant a polyethylene glycol, using a nonionic gelling agent such as hydroxy ethyl cellulose, combining a compatible dental abrasive, preferably hydrated alumina, calcined alumina or hydrous silica gel, and maintaining a pH below about 6, and preferably between 5 and 6, preserves and enhances the antimicrobial activity of the hexetidine in combination with the soluble zinc salts (Zn++) and the fluoride (F-) in the dentifrice.
The prior art does not disclose a cosmetically and therapeutically antiplaque dentifrice containing as the essential ingredients an antimicrobial combination of hexetidine, a zinc salt and a fluoride-providing compound; a surfactant; a polyethylene glycol humectant; a nonionic gelling agent; and a compatible dental abrasive, and said dentifrice having a pH below about 6.